The invention concerns the mounting of an adjustable rotor blade on the rotor hub of a wind power installation with a rolling bearing for the transmission of high axial forces and large flexural moments with small relative movements between the co-operating bearing components in an adjusting drive pivot bearing between the rotor hub and a rotor blade of a wind power installation.
A ball-mounted rotary connection is known for excavators, rotary cranes or the like from DE 27 52 487 B1. As is known, the advantage of rolling bearings lies in the low level of (frictional) resistance which they oppose to the relative movement between the co-operating bearing components. That applies also and precisely in regard to pivot bearings as are used for example in adjusting drives, because there, in contrast to plain bearings, it is not necessary to overcome the static friction resistancexe2x80x94which is higher than the sliding frictionxe2x80x94in each pivotal movement out of the rest position. On the other hand a multi-point bearing reacts substantially less sensitively than a plain bearing to high axial forces and in particular large flexural moments. The influence thereof becomes particularly serious if the rolling bearing must be of a large diameter and the flexural moments result in a radial relative displacement of the bearing races or rings. Thus, in the case of a ball bearing assembly, assuming an osculation of 6% (deviation of the raceway diameter from the ball diameter) the ball pressure angle in the raceway alters from 45xc2x0 to 85xc2x0 when the bearing races are radially displaced relative to each other by 0.56 mm; the balls are therefore only still rolling on the edges of the bearing races.
The variation in the pitch angle of the rotor blades of a wind power installation relative to the rotor hub thereof represents such an adjusting drive; as is known, for reasons of efficiency and safety, the pitch angle has to be altered in dependence on the respective wind speed during rotation of the rotor. DE 196 34 059 discloses a rotor blade mounting for a hollow rotor blade, the mounting comprising two ball bearings of the same diameter, which are displaced in the axial direction, wherein the common join line extends concentrically with respect to the axis of rotation so that radial forces can be carried well, but axial forces can be only limitedly carried. In operation however each rotor blade is subjected to considerable forces in the direction of its longitudinal axisxe2x80x94about which the rotor blade is pivoted upon adjustment of the pitch anglexe2x80x94and the rotor blade is also exposed to considerable flexural moments which the pivot mounting of the rotor blade on the rotor hub has to withstand, irrespective of frequent pivotal movements.
The object of the present invention is to provide a rotor blade mounting which satisfies that demand.
Based on the arrangement described in the opening part of this specification, that object is attained in a rolling bearing comprising a bearing race for the one co-operating bearing component, which bearing race receives in positively locking relationship two radially mutually displaced rows of rolling bodies, and a bearing race for the other co-operating bearing component, which embraces them in a U-shape in cross-section, wherein the bearing race for the rotor blade forming the other co-operating bearing component comprises two rings of different diameters which are fixed independently of each other to the rotor blade. That arrangement affords on the one hand a practically three-race rolling bearing whose central race which is secured to the other co-operating bearing component, upon the occurrence of flexural moments (and axial forces) receives from the two outer races (or race portions of the embracing bearing race) pressure forces in directions which extend more or less perpendicularly to each other and which are thereby automatically rendered symmetrical, and the pressure forces therefore respectively remain in the central region of the bearing raceway quadrants, while on the other hand the forces from the rotor blade are simultaneously applied to the two outer races (or race portions) and this therefore provides for more uniform loading of the mounting and the rotor blade root. The formation of the embracing bearing race from two outer races and a circular ring or race connecting them is known from EP 0 158 015 A2.
Preferably the circular root of the hollow rotor blade is forked in the form of two shell portions and each shell portion is fixed to one of the two races of the one bearing race. The two rows of rolling bodies are in particular arranged concentrically relative to each other. It is however also possible for them to be axially displaced.